QGIS Coordinate System – How to Set CRS in QGIS?

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QGIS does not recognize .prj file, which is part of a shapefile.

ArcMap does automatically recognize .prj file, when you add shapefile to ArcMap layer, you click property, coordinate tab, you can see the correct CRS (coordinate reference system) already set there.

However, QGIS failed to recognize .prj file, instead you have to manually set CRS in QGIS.

But how?

Best Answer

Qgis recognise .prj files but "do not provide the complete projection parameters as used in QGIS". Qgis generate .prj file as well to be compatible with Esri software and store is own projection parameter under .qpj file.

From the qgis doc

Problem loading a shape .prj file

If you load a shapefile with a .prj file and QGIS is not able to read the coordinate reference system from that file, you will need to define the proper projection manually within the General tab of the Layer Properties dialog of the layer by clicking the [Specify...] button. This is due to the fact that .prj files often do not provide the complete projection parameters as used in QGIS and listed in the CRS dialog.

For the same reason, if you create a new shapefile with QGIS, two different projections files are created: a .prj file with limited projection parameters, compatible with ESRI software, and a .qpj file, providing the complete parameters of the used CRS. Whenever QGIS finds a .qpj file, it will be used instead of the .prj.

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